Holyoke is a city in Hampden County, Massachusetts, United States, that lies between the western bank of the Connecticut River and the Mount Tom Range. As of the 2020 census, the city had a population of 38,247. Located 8 miles (13 km) north of Springfield, Holyoke is part of the Springfield Metropolitan Area, one of the two distinct metropolitan areas in Massachusetts.

Holyoke is among the early planned industrial cities in the United States. Built in tandem with the Holyoke Dam to utilize the water power of Hadley Falls, it is one of a handful of cities in New England built on the grid plan. During the late 19th century the city produced an estimated 80% of the writing paper used in the United States and was home to the largest paper mill architectural firm in the country, as well as the largest paper, silk, and alpaca wool mills in the world. Although a considerably smaller number of businesses in Holyoke work in the paper industry today, it is still commonly referred to as "The Paper City". Today the city contains a number of specialty manufacturing companies, as well as the Massachusetts Green High Performance Computing Center, an intercollegiate research facility which opened in 2012. Holyoke is also home to the Volleyball Hall of Fame and known as the "Birthplace of Volleyball", as the internationally played Olympic sport was invented and first played at the local YMCA chapter by William G. Morgan in 1895.

While managing the Holyoke Testing Flume in the 1880s, hydraulic engineer Clemens Herschel invented the Venturi meter to determine the water use of individual mills in the Holyoke Canal System. This device, the first accurate means of measuring large-scale flows, is widely used in a number of engineering applications today, including waterworks and carburators, as well as aviation instrumentation. Powered by these municipally-owned canals, Holyoke has among the lowest electricity costs in the Commonwealth, and as of 2016 between 85% and 90% of the city's energy was carbon neutral, with administrative goals in place to reach 100% in the future.